[Degeneration of ponto-cerebellar tract visualized by diffusion tensor imaging in multiple system atrophy]

We visualized ponto-cerebellar tracts projecting through the middle cerebellar peduncle of 3 patients with early stage multiple system atrophy (MSA), 3 patients with advanced stage MSA, and a healthy control using diffusion tensor imaging (DTI) on 1.5T magnetic resonance imaging (MRI). We also examined whether the location of the degenerated ponto-cerebellar tracts coincided with that of the transverse part of the so-called "hot cross bun sign (HCB)" on MRI. DTI successfully demonstrated the degeneration of ponto-cerebellar tracts in MSA patients. The tracts in advanced stage MSA patients appeared more sparse than those in patients of the early stage. High apparent diffusion coefficient (ADC) values and low fractional anisotropy (FA) values also indicated the degeneration of the ponto-cerebellar tracts in MSA patients. The tracts in the ventral pons were more sparse than those in the central pons. The location of the degenerated ponto-cerebellar tracts of the central pons appeared to coincide with that of the transverse part of HCB. Visualization of degenerated ponto-cerebellar tracts that cross the ventral pons using DTI might be useful for the early diagnosis.